During fabrication of a semiconductor, the use of special gases is usually required for different processes. For example, NH3 and SiH2Cl2 are employed as raw materials for forming a silicon nitride layer, NH3 and O2 are employed for wafer cleaning, HF is used for etching silicon dioxide (SiO2), and so on. However, if these special gases contain metal particles, even though in a very small amount, the metal particles may possibly fall on a surface of an object to be processed and cause yield loss.
Therefore, online monitoring particle contamination in a conveying gas becomes a great challenge. Recently, there are commonly used apparatuses for monitoring particle contamination, e.g., a scanning mobility particle sizer (SMPS) or a fast mobility particle sizer (FMPS); however, as long as a particle size is smaller than a nanometer degree, collection efficiency thereof will be reduced down to 20% or less.
Therefore, a detection technique using a single particle inductively coupled plasma mass spectrometry (sp-ICPMS) is currently developed. Nevertheless, such detection technique is not yet actually applied online, and no researches for the monitoring of the particle contamination in special gases are conducted.